sock_diag: Generalize requests cookies managements

The sk address is used as a cookie between dump/get_exact calls.
It will be required for unix socket sdumping, so move it from
inet_diag to sock_diag.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp_diag.c b/net/ipv4/udp_diag.c
index fe9db86..69f8a7c 100644
--- a/net/ipv4/udp_diag.c
+++ b/net/ipv4/udp_diag.c
@@ -57,7 +57,7 @@
 	if (sk == NULL)
 		goto out_nosk;
 
-	err = inet_diag_check_cookie(sk, req);
+	err = sock_diag_check_cookie(sk, req->id.idiag_cookie);
 	if (err)
 		goto out;